Is there even a full road system all the way there? I have thought about the same kinda trip but havent really thought it possible

There is only a few miles of road missing in Panama to link the Central to the South America. The reason for that is not practical but political, the USA has very strong influence in Panama since the construction of the canal, not having a road would force the use of the canal thus generating income to its administrators (USA) and would also prevent a migration route and drug route. But the trip is possible an easy, just get to the canal, place your car on a ship and send it to Venezuela, Colombia or Ecuador and proceed from there.